Viscometers
Viscometers or viscosimeters are important to many industries, including the adhesive, biotech, chemical, food, paint, petroleum, and pharmaceutical industries.
What Is a Viscometer?
Viscometers are instruments used to measure viscosity, the internal friction of the layers of a liquid in motion. An example is the slower flow of syrup from a container — syrup is more viscous than water.
How Is Viscosity Measured?
In general, viscometers move an object through a stationary fluid or move the fluid past a stationary object to measure the friction between the fluid and the object or surface. Viscometers measure using a single flow condition.
What Are the Different Types of Viscometers?
Glass capillary viscometers or Ostwald or Ubbelohde viscometers consist of a U-shaped glass tube held vertically in a controlled temperature bath. Liquid is drawn by suction into the upper bulb and allowed to flow down into the lower bulb. You calculate viscosity by measuring the amount of time it takes for the liquid to move between two marks.
Falling ball viscometers measure the time it takes for a sphere of a known size and density to descend through a stationary liquid. This can be done electronically for opaque fluids.
Rotational viscometers use the concept of torque to measure the effort required to turn a disk or bob in a fluid. Rotating bobs are more common, rotating cups reduce the likelihood of vortex formation, and "cone and plate" viscometers create a constant shear rate at any speed.